Resistor for spark plugs



RESISTOR FOR SPARK PLUGS Filed Aug. 4, 1942 INVENTOR.

'1711215 @16 5575/? L SToF/FEL 73am/ 71m/ 9L @Pda/n Patented Feb. 13, 1945 RESISTOR FOR SPARK PLUGS Lester L. Stoffel, Lakewood, Ohio, assignor to The Ohio Carbon Company, Cleveland, Ohio, a corporation of Ohio Application August 4, 1942, Serial No. 453,520

I6, and a housing I'I of insulating material there 4 Claims.

This invention relates to resistors which are adapted particularly for use Lin connection with spark plugs of internal combustion engines so as to minimize interference on radio reception. One form of resistor heretofore in general use includes an'insulated casing into one end of which a current conducting plug is threaded. A screw projects outwardly from the plug and is adapted to be threaded into a flexible conductor and to expand the same against the wall of the housing for making a rigid current-conducting connection therewith. The housing is usually of a resinous material and the end thereof opposite the flexible lead is adapted to be attached to the projecting current conducting shank of a spark plug.

Considerable difficulty has heretofore been experienced in the operation of military vehicles, such as tanks or trucks, in maintaining a tight connection between the threaded plug and the resistor housing, because of the excessive vibration to which the vehicles are subjected in use. The vibration incident to a nearby explosion, and also the vibration from travel over uneven ground has caused the threaded part to become loosened in the housing, and has interfered with the proper operation of the electrical distribution and communication system.

An object of the present invention is to so construct the current conducting plug that it may still be used in the customary way, and yet will be securely locked against rotation with respect to the housing, notwithstanding the vibrations,

to which the vehicle may be subjected in normal use. An object additionally is to make a structure which can be assembled `in an economical' manner.

Referring now to the drawing, Fig. 1 is a side View of a portion of a spark plug having a resistor embodying my invention attached thereto and shown in longitudinal section thereon; Fig. 2 is an end view of the resistor; Fig. 3 is a perspective view of the threaded plug, Fig. 4 is a side view, partly in section, of the plug and showing diagrammatically its application to the housing in a manner contemplated by the present invention, and Figs. 5 and 6 are side views showing modified forms of the conductor plug.

In the drawing, ID represents the current conductingshank of a spark plug II, and I2 indicates the flexible current conducting lead which is adapted to be connected to the spark plug conductor Il) through the medium of the resistor unit, indicated in general at I5.

The resistor unit includes a resistance element for. The housing has a recess 25 extending longitudinally thereof for holding the element and for protecting the connection between the element and the lead I2. A yieldable current conducting coil I 8 may project laterally from the housing at one end thereof for attachment to the spark plug shank, while a current conducting plug I9 may be disposed within the housing at the end opposite the coil for enclosing the resistance element within the housing and for making a current conducting connection with the lead I2.

As shown in Fig. 3, the plug has a radially extending disc 20 intermediate the ends thereof and has a threaded portion 2I on one side which is adapted to engage a correspondingly threaded portion within the housing I1, and has a tapered and threaded portion 22 on the other side for entering the end of the conduit I 2 and expanding it against the wall of the housing.

A modification of the plug is shown in Fig. 5, wherein the portion 2l is knurled instead of threaded, and wherein the remaining parts are substantially the same as shown in Fig. 3. A further modification is shown in Fig. 6, wherein the portions 2|] and 2I are merged into a cylindrical surface 3D which is adapted to be pressed into firm engagement with the wall of the recess within the housing.

To prevent loosening of the plug, I prefer to make the flange 20 suiiiciently small in diameter that it may clear the Wall of the recess 25 upon insertion of' the plug into the housing. Addi'- tionally, I propose to make the housing of resinous material which preferably is soft enough to permit the metal of the flange to be pressed into the housing, and which has a shoulder 26 against which the disc is adapted to engage whenever the portion 2| is firmly connected to the housing. A seal is effected between the disc and housing by swaging the disc outwardly and radially as by means of a spinning tool applied in the direction of the arrows in Fig. 4. This may be accomplished either by rotating the spinning tool or by rotating the housing in a machine. The disc may thus be extended outwardlyy and radially until the diameter thereof is larger than the internal diameter of the recess 25, as shown by the broken lines 28a in Fig. 4. During the enlarging operation, the metal of the disc will enter the material of the housing and become firmly embedded therein.

Where the modified form of plug, shown in Fig. 6 is used, the cylindrical portion 30, which may have a smooth exterior surface, is pressed nrmly into the housing and the end edge 3l is swaged over, as by a spinning operation, until the metal thereof is forced into the material of the housing. Such interconnection between the plug andhousing makes a joint which is sufilciently resistive against rotation, or other movement of the plug with reference to the housing, so as to prevent' loosening of the connection under severe vbratory conditions.

I claim:

1. A method of fastening a current conductingl plug to an insulated housing of a resistor unit, comprising inserting the plug into the housing and enlarging the plug radially by pressure against the plug sufficiently to embed a portion of it into the housing.

2. A method of fastening an electrical conductor to a housing of insulating material in a resistor unit, comprising exerting pressure against the member in a substantially axial direction and progressively around the periphery of a portion thereof sumciently to enlarge the plug radially, and thereby swaging a portion of the member against the housing, suiciently to hold it against movement with reference to the housing.

3. In a. resistor unit, the combination of a housing having a recess therein, a resistance element and a current conducting plug within said recess, said plug having a portion thereof swaged outwardly sufficiently to make the cross sectional area thereof greater than that of the normal cross section of the recess in the housing in which it is located, whereby the plug is embedded in the housing and held against movement with relation to the housing.

4. In an electrical resistor unit, a housing of insulating material having` a longitudinally extending recess therein, a resistance element disposed within the recess, said recess having an enlarged portion adjacent one end of the housing, a conductor member having a portion thereof in close fitting engagement with the smaller portion of the recess in the housing and having another portion extending radially, the radially extending portion being normally of slightly smaller cross section than the cross section of the larger portion of the recess, whereby the member may be inserted into said larger portion from one end of the housing, said radially extending portion being swaged adjacent its marginal edge to make the cross sectional area thereofy larger than the normal cross section of said recess, whereby the member is prevented from moving freely out of the recess.

LESTER L. STOFFEL. 

